Blender can't add armature anymore
To help troubleshooting, select the mesh and check what's on its parent field.

Then, as thibsert suggested, try to use the menu instead of the shortcut, it looks like you're telling the computer "Alt P" and not "Ctrl P". Did you switch phisically the two buttons on your keyboard? Or wrongly mapped them in your OS?

If the problem persist, try uploading your file.